POJ 2352 HDU1541 Stars(树状数组)

题意：二维平面给定n个点的坐标，然后要你输出每个点的“等级“。每个点的等级是它的左下放的点个数(包括正下放和正左方的点)。即要你输出对于每个点(x,y)来说，有多少点的坐标(xi, yi)满足xi<=x且yi<=y。

思路：题目给出的坐标中已经是按y升序排列，那么其实只用考虑x轴，那么显然就是在前面的点中找比自己小的。

Trick：注意的是累加的时候while循环的条件要改一下，因为我们这里是用x轴坐标的值作为c数组的下标，而x最大到32000，而不是n。

#include <cstdio>
#include <queue>
#include <cstring>
#include <iostream>
#include <cstdlib>
#include <algorithm>
#include <vector>
#include <map>
#include <string>
#include <set>
#include <ctime>
#include <cmath>
#include <cctype>
using namespace std;
#define maxn 32000+10
#define LL long long
int cas=1,T;
int c[maxn];
int L[maxn];
int n;
int lowbit(int i)
{
	return i&(-i);
}
int sum(int i)
{
	int ans = 0;
	while (i)
	{
		ans +=c[i];
		i-=lowbit(i);
	}
	return ans;
}
void add(int i,int d)
{
	while (i<=maxn)
	{
		c[i]+=d;
		i+=lowbit(i);
	}
}

int main()
{
	//freopen("in","r",stdin);
	while (scanf("%d",&n)!=EOF && n)
	{
		memset(c,0,sizeof(c));
		memset(L,0,sizeof(L));
		for (int i = 1;i<=n;i++)
		{
			int x,y;
			scanf("%d%d",&x,&y);
			x++;
			L[sum(x)]++;
			add(x,1);
		}
		for (int i = 0;i<n;i++)
			printf("%d\n",L[i]);
	}
	//printf("time=%.3lf",(double)clock()/CLOCKS_PER_SEC);
	return 0;
}

Description

Astronomers often examine star maps where stars are represented by points on a plane and each star has Cartesian coordinates. Let the level of a star be an amount of the stars that are not higher and not to the right of the given star. Astronomers want to know the distribution of the levels of the stars. 

For example, look at the map shown on the figure above. Level of the star number 5 is equal to 3 (it's formed by three stars with a numbers 1, 2 and 4). And the levels of the stars numbered by 2 and 4 are 1. At this map there are only one star of the level 0, two stars of the level 1, one star of the level 2, and one star of the level 3. 

You are to write a program that will count the amounts of the stars of each level on a given map.

Input

The first line of the input file contains a number of stars N (1<=N<=15000). The following N lines describe coordinates of stars (two integers X and Y per line separated by a space, 0<=X,Y<=32000). There can be only one star at one point of the plane. Stars are listed in ascending order of Y coordinate. Stars with equal Y coordinates are listed in ascending order of X coordinate.

Output

The output should contain N lines, one number per line. The first line contains amount of stars of the level 0, the second does amount of stars of the level 1 and so on, the last line contains amount of stars of the level N-1.

Sample Input

5 1 1 5 1 7 1 3 3 5 5

Sample Output

1 2 1 1 0